1. Field of the Invention
The field of the invention is radio frequency communications.
2. Description of the Background
Transmission of data via radio signals is an effective means of communication to a variety of devices located within range of the signal. An advertiser or other provider of the data (including content) may pre-select a radio frequency carrier type (e.g. FM sub-carrier, AM sub-carrier, Cellular etc . . . ), a broadcasting station (e.g. KUS FM), and/or a frequency over which the data will be broadcast (e.g. 102.7 MHz @ (57 kHz RBDS) based on the geographic location of the target audience. The particular frequency maybe chosen because of its popularity with the target audience, its spectrum availability, the type or device that will receive the signals, and importantly because it's signals will cover (i.e. reach) the targeted audience.
Covering the target audience is deemed essential, and since many applications of radio frequency (RF) communication target an audience existing within a relatively small geographic area, often coverage is not a problem. For example, it is common to broadcast music or news over a pre-selected frequency to all areas of an office building. Pre-selection of the frequency and pre-tuning of the receivers to that frequency is a relatively easy process. Another example of an RF communication within a relatively small area is a radio controlled car that is set to receive signals broadcast over a pre-selected frequency. Yet another example is taught by U.S. Pat. No. 6,298,218 to Lowe et al. (October 2001). The '218 patent targets audiences within a few feet of the transmitting device. This is exemplified by an athletic club environment in which a user device receives different broadcasts on different frequencies depending on his proximity to specific pieces of gym equipment having transmitters. Thus, those applications that target audiences over a relatively small area typically work well with pre-selection of the frequency and the station. Coverage becomes an issue and complications arise, however, when the target audience is spread over an area that encompasses more than one frequency, station, and/or band. These complications are due in part to the necessity to pre-select many, perhaps hundreds or thousands, of frequencies and stations in order to cover the entire target audience. Thus, pre-selection of frequencies becomes extremely burdensome when a wide spread audience has been targeted.
The need to employ several stations simultaneously is addressed by U.S. Pat. No. 4,517,562 to Martinez (May 1985), however the '562 patent still does not solve or even recognize problems related to the difficulty of scheduling and coordinating communications over a wide spread area. These problems are exacerbated by competition for available RF spectrum and perhaps the distance between a data provider and a data recipient.
There is a need for systems and methods which facilitate use of radio signals to communicate to devices that may be spread over a relatively large area.